MKIIA Airbox & Silencers

The 850 MKIIA I'm restoring came with the original plastic airbox, and a pair of blackcap silencers which are in very good condition.
And that's the problem!
I can't (easily) justify buying a pair of pea-shooters while I've got a 'decent' pair of silencers already.

I have a lingering suspicion that this may not be the, ...er....'most lively'..? combination ever fitted to a Commando.

Does anyone run this setup, or have a bike modded from this configuration to make the comparison?
Is changing the silencers essential? Is the airbox part of the problem?
Is retrofitting the breadbox filter a big hassle?

I'm not looking for an ultimate performance solution (I've got the D***ti for that), and I am looking for a pleasant bike to ride...but if there are gains to be had for little effort, it would be plain churlish not to go for them!

Hi, as everybody throw those parts when they were out of fshion, they are now quite rare!!!so keep them.
the air box was part of the performance reducing system, but the black cap were not..........if I was you , I install the 750 air filter and keep the black caps but with 750 pipes (no more hassle with the junction crossover.......) , my two pence.

Is retrofitting the breadbox filter a big hassle?

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If the Commando was built around the placement of the horn, the second item they installed on a MkIIA or MkIII was that plastic air box! :shock:

As MarinAtlas says they are becoming quite rare. And there are differences between the MkIIA and MkIII! If you decide to replace the airbox, resist the temptation to cut it out.

Installing the early air box may also require using a non-MkIIA battery box as the rear plate of the air box bolts to the battery box. Of course, you could also use the K&N clamp on filter.

If I recall, neither of these boxes will come out in one piece with the engine in place. I personally have never had to remove one so this is hearsay to me. My Mk3 had lost its airbox long before I obtained it.

I'm running my MK2A Interstate with black cap silencers and the black plastic air box. Two things are not original, I use 750 exhaust pipes and I have drilled 3 ea 10 mm holes in each end cap of the silencers.
The bikes performance is great, no problems to keep up with other Commandos, nice sound (can be tuned by the size of the drilled holes).
The airbox is most certainly "filling out" the frame and does not help to access various things oraound it but that's the only negative thing I can think of.

Cheers,
Per

I agree that it would be nice to keep them as most are now gone.

I run the Plastic box with peashooters, the peashooters seem to make the bike perform well, can't see where the plastic box gets its bad press from as if I leave the oiled foam element out the bike runs much the same. When I put the peashooters on I had to go from 230 to 260 on the main jets to get the full top end back so IMHO its the black cap silencers that are the power drain. I do not run with the rubber baffles in the two curved inlets in the bottom of the plastic box, just have the filter element in there.

In the 70s i had a 850 mk2 with black cap mufflers, changed it to decibel mufflers a major improvement. I now have a mk2a with plastic airbox but peashooter as i have not been able to find a good set of black caps. And yes mk2a airboxes are different to mk3

possm said:

And yes mk2a airboxes are different to mk3

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The only apparent difference between the MkIIA and MkIII airboxes that I can think of, would be the lack of any ignition switch bracket on the MkIII box?

The only apparent difference between the MkIIA and MkIII airboxes that I can think of, would be the lack of any ignition switch bracket on the MkIII box?

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And the side panel mounting Dzus receiver? The MkIIA panel fastener is at the bottom, the MkIII at the top?

Ron L said:

And the side panel mounting Dzus receiver? The MkIIA panel fastener is at the bottom, the MkIII at the top?

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Yes, of course you are right, Ron, the 'A' side panel Dzus fastener is fixed to a bracket on the 'A' type battery carrier.

I don't think there's any design difference between the two airboxes that would be likely to affect performance?